In recent years, thin film solar cells which are formed from gases as a raw material by a plasma CVD method receive attention. Examples of the thin film solar cells include silicon-based thin film solar cells made of a silicon-based thin film, CIS compound or CIGS compound thin film solar cells and the like, and development of these solar cells are accelerated and their quantities of production are increasingly enlarged.
These thin film solar cells are formed by laminating a transparent electrode, a photoelectric conversion layer, and a backside electrode on a substrate by a plasma CVD method, a sputtering method, or a vacuum evaporation method. In the thin film solar cell, since a layer thickness of the photoelectric conversion layer sandwiched between two electrodes is small, a pin hole produced in the photoelectric conversion layer readily causes short circuit between electrodes, thereby deteriorating power generation characteristics.
For the purpose of recovering such characteristics of a thin film solar cell, there is proposed a method and apparatus for performing reverse biasing in which short-circuit (pinhole) portions are dissipated to be removed or oxidized to be insulated through joule heat produced then by applying a reverse bias voltage between the electrodes of a solar cell.
For example, Patent Document 1 discloses a method and apparatus for removing short-circuit portions of a solar cell, in which with respect to a solar cell in which a plurality of strip-shaped solar cells formed by sequentially laminating a first electrode layer, a photoelectric conversion layer, and a second electrode layer on an insulating substrate are connected in series, short-circuit portions are removed by applying a voltage of a withstand voltage or less to both positive and negative electrode of the solar cell in a reverse direction. In this case, an applying member having a plurality of point-like, one or more linear, or one or more planar contact portions is brought into contact with a backside electrode of two solar cells adjacent to each other. Since a backside electrode of one solar cell is connected to a transparent electrode of the other solar cell, a voltage below a withstand voltage is applied in a reverse direction to the other solar cell.
It is described that in accordance with this method and, apparatus for removing short-circuit portions, setting and control of an applied voltage are easy and stable since by using an applying member formed of a plurality of probes, one or more linear, or one or more planar applying members, distances between the applying members and the short-circuit portions are reduced to decrease a voltage drops at the first electrode and at the second electrode, and therefore removal of the short-circuit portion can be ensured.    Patent Document 1: Japanese Unexamined Patent Publication No. 10-4202